PROJECT SUMMARY. Epidemiologic and randomized clinical studies suggest that low vitamin D levels are associated with decreased bone mineral density and increased fracture risk. Additionally, vitamin D plays a major role in various metabolic processes and deficiency has been implicated in childhood rickets, osteoporosis, type II diabetes, and a variety of cancers. Since 1988, vitamin D levels have been decreasing across the U.S. population, by approximately 10%. There is a significant disparity in vitamin D status among non-Hispanic Blacks, Mexican Americans, and non-Hispanic whites in the United States, with non-Hispanic Blacks having the highest prevalence of vitamin D deficiency (<12 ng/ml), followed by Mexican Americans. Both groups also have a higher prevalence of vitamin D inadequacy (12-20 ng/ml) than non-Hispanic whites. Randomized clinical trials have shown that adequate vitamin D intake through dietary supplementation in populations at risk for nutritional deficiency can prevent fragility fractures and may improve metabolic disease outcome. Supplementation is thus an easy and inexpensive mode of treatment; however, there does not currently exist a point-of-care, cost effective method of measuring a patient?s vitamin D status. Serum vitamin D is measured clinically using plate- based enzyme-linked immunosorbent assay (ELISA) tests, which can take one to three hours and require a laboratory setting. BreviTest Technologies LLC is developing a portable analyzer to perform a rapid, quantitative ELISA test within a 10-minute run time. The sample is loaded into a microfluidics cartridge, and an automated mechanism controls the movement of antibody- conjugated magnetic nanoparticles through successive fluid wells, where enhanced mixing patterns substantially reduce the time required for each ELISA step. This innovative approach enables the implementation of a rapid, portable, fully automated ELISA test with accuracy comparable to a standard laboratory ELISA. In this SBIR Phase I project, we will perform the following specific aims: (1) Develop and optimize a rapid ELISA assay for total vitamin D using the BreviTest portable analyzer; and (2) Perform proof-of-concept testing to detect total vitamin D in simulated blood samples using the BreviTest portable analyzer. Deployment of a point-of- care vitamin D test in retail pharmacies and health clinics, particularly in at-risk communities, will enable easy assessment of vitamin D status, which will facilitate targeted dietary supplementation to address vitamin D deficiency in underserved populations.